Grid electrode for electrical discharge tubes



April 12, 1966 E. s. DEN DULK GRID ELECTRODE FOR ELECTRICAL DISCHARGE TUBES Filed June 26, 1962 INVENTOR ERNST S. DEN DULK AGENT United States Patent 1 3 Claims. (a. 313-345 The invention relates to a grid electrode for electric discharge tubes, which electrode is manufactured according to the method described in Netherlands patent specification 89,848, and which consists of a frame constituted by two supporting rods on which a grid wire is tautly wound, and two cross bars having in general a rectangular cross-section and being provided in the proximity of the ends of the grid electrode, while on each grid end at least one of the cross bars is welded on one of the supporting rods at some distance from its end, so that it has a part which projects outside the frame. Both the supporting rods and the cross bars and the grid wire c sist of molybdenum. In this known construction, the grid wire is connected to the supporting rods with a vitreous cement or by means of a welded rod provided across the grid wire. However, this connection of the grid wire is somewhat complicated.

A considerable simplification can be obtained if in such a grid according to the invention the supporting rods consist of nickel, while the ends of the grid wire are clamped by bending the projecting ends of the cross bars consisting of molybdenum about the supporting rods after winding the grid wire.

This has only become possible by the use of nickel supporting rods. In the known frame grids, in which the supporting rods and also the cross rods consist of molybdenum, the molybdenum becomes very brittle as a result of welding, so that bending of the projecting ends of the cross rods substantially invariably results in fracture of these ends and consequently in a high number of rejects. Therefore, clamping of the grid wire by bending these ends of the cross bars was not possible in practice. Because, according to the invention, the supporting rods consist of nickel, it appears that the Welding temperature lies so much lower that the molybdenum of the cross bars remains sufiiciently ductile to render bending possible as such. The crossed rods must consist of molybdenum because its coefficient of expansion must be as much as possible equal to that of the grid wire-s, since otherwise the tensile strength in the grid wires would vary too strongly with the temperature of the grid.

Although the use of nickel supporting rods for grids was known per se, this material was so far not used for grids with tautly strained wires, since it was feared that the rods would be too weak and would deflect. It has appeared, however, that this drawback in general only holds for the thinner rods for the first and second grids of an electrode system. The supporting rods for these grids must be suitably profiled so that the resistance against deflection in a direction parallel to the grid wires is sufficiently increased.

The invention will now be described with reference to the accompanying drawing, in which FIG. 1 is a continuously wound grid before the grids are separated,

FIG. 2 shows the end of a grid according to the invention, and

FIG. 3 is a plan view of such a grid.

FIG. 4 is a plan view of another embodiment and FIGS. 5 and 6 are a front view and a plan view respectively of still another embodiment according to the invention.

Two continuous grid supporting rods 1 in FIG. 1 are connected by cross rods 2 which in this case extend about one of the supporting rods 1 and the .free ends 3 of which are welded on the other supporting rod 1 at some distance from the end indicated by a cross.

In the above older construction, both the rods 1 and the cross rods 2 consisted of molybdenum. The grid wire 4 is wound across the rod 1 and hooked behind a projecting end 3 of a cross rod 2 at the end of a grid and conducted to the beginning of the following grid via the rod 2, so that the portion between the grids has no turns which would have to be removed afterwards.

In this known construction, the grid wire 4 is provided on the supporting rods 1 between the grids by means of glass or by welding-on a strip. The grids are separated by cutting the rods between two grids.

According to the invention, the rods 1 consist of nickel and it now appears possible to bend the ends 3 of the molybdenum cross bars 2 about the rods 1, so that the grid wire 4 is clamped (FIGS. 2 and 3) without these ends breaking off. The end of the grid wire is indicated b 5.

Since the nickel rods 1 are much softer than molybdenum rods, :a suitable cross profile 8 will have to be used in many cases, as indicated, for example, in FIG. 4, in order to obtain a sufficient rigidity in a direction parallel to the grid wires 4. In FIG. 4, separate cross bars 6 are provided. One end 7 clamps the wire end 5. The other end 7 is preferably bent also, as indicated by an arrow. The flat sides of the supporting rods 8 have the advantage that they facilitate the welding of the cross rods 6 and cause a certain damping of the grid wires because these wires shift along the fiat face when vibrating, so that the microphonic effect of the grids is decreased. However, the use of such profiled supporting rods was already known.

The invention is also particularly suitable for the case known per se .in which two grids are wound across each other. Across the wires 4, a second grid 9 is wound in the case of FIGS. 5 and 6, which grid has .a pitch, for example, which corresponds to that of a screen grid of the electrode system. Then the wires 9 may shadow the wires of the positive screen grid in order to decrease the screen grid current without it being necessary for this screen grid to have a pitch which is as small as that of the grid 5 which is formed by the wire 4, or conversely. The four ends 5 and 10 respectively may then each be clamped behind a separate projection 3 or 7 so that it is not necessary to clamp two ends of a wire under one projection.

It is clear that many other constructions of grids according to the invention are possible.

What is claimed is:

1. A grid electrode for an electric discharge tube comprising a pair of spaced support rods, a pair of molybdenum cross-bar members placed cross-wise in spaced relationship over the stay-rods, a grid wire helically and tautly wound over the stay-rods between the cross-bar members, the ends of said grid wire passing and being clamped between the ends of the cross-bar members and the stayrods, the ends of said cross-bar members being bent around the support rods to firmly secure the ends of the grid wire.

2. A grid electrode for an electric discharge tube comprising a pair of spaced support rods, a pair of molybdenum cross-bar members placed cross-wise in spaced relationship over the stay-rods, a grid wire helically and tautly wound over the stay-rods between the cross-bar members, the ends of said grid wire passing between the ends of the cross-bar members and the stay-rods, the ends of said cross-bar members being bent around the support rods to firmly secure the ends of the grid wires, the support rods ends of the cross-bar mernbers are bent about the stayrods.

3. A grid electrode for an electric discharge tube compris-inga pair of spaced nickel support rods, a pair-of molybdenum cross-bar members placed cross-wise in spaced relationship over the stay-rods, a grid wire helically and tautly wound over'the stay-rods between the cross bar members, the ends of said grid wire passing between the ends of the cross-bar members and the stay-rods, the ends of said cross-bar members being bent around and en: gaging the support rods to firmly secure the ends of the grid wire; the support rods having a cross-section which v 4 t resists 'de'formatioh'when theends of the crossbar members are bent around the stay-rods.

References Cited by the Examiner UNITED STATES PATENTS 2/1931 Grebel 3 13350 FOREIGN PATENTS 1,041,605 10/1958 Germany.

1,113,036 8/1961 Germany.

JOHN W HUCKERT, Primary Examiner.

GEORGE N. WESTBY, Examiner. 

1. A GRID ELECTRODE FOR AN ELECTRIC DISCHARGE TUBE COMPRISING A PAIR OF SPACED SUPPORT RODS, A PAIR OF MOLYBDENUM CROSS-BAR MEMBERS PLACED CROSS-WISE IN SPACED RELATIONSHIP OVER THE STAY-RODS, A GRID WIRE HELICALLY AND TAUTLY WOUND OVER THE STAY-RODS BETWEEN THE CROSS-BAR MEMBERS, THE ENDS OF SAID GRID WIRE PASSING AND BEING CLAMPED BETWEEN THE ENDS OF THE CROSS-BAR MEMBERS AND THE STAYRODS, THE ENDS OF SAID CROSS-BAR MEMBERS BEING BENT AROUND THE SUPPORT RODS TO FIRMLY SECURE TH ENDS OF THE GRID WIRE. 